Habitat

Crocodylus mindorensis seems to prefer small wetlands, but has also been found in shallow natural ponds and marshes, man-made water reservoirs, shallow narrow creeks, littoral creeks and mangrove areas, and faster-flowing larger rivers in the mountains up to 850 m. They have been observed in both the Sierra Madre and Cordillera Mountains in fast flowing rivers with rapids and deep pools lined by limestone cliffs. The cliffs have caves thought to be used as hiding places. The Philippine crocodile has also been found to make burrows in sandy and clay river banks. (Van Weerd, et al., 2006; Van Weerd, 2010)

Physical Description

Crocodylus mindorensis is a relatively small species of freshwater crocodile. Hatchlings are golden-brown dorsally with transverse dark stripes, and are white on their ventral side. As they age the brown darkens. Compared to other crocodiles they have a relatively broad snout and heavy dorsal armor. The record length is 3.02 m, but most individuals are much smaller. Males mature at about 2.1 m, females at 1.3 m.

Development

Like all crocodilians, C. minodorensis exhibits temperature dependent sex determination. Utilizing artificial incubation, it has been observed that mostly females are produced at 30 to 31°C and mostly males at 33°C. In captivity, egg fertility rates were found to be 56% and 57% in Palawan and Negros,respectively, and hatching rates of fertile eggs were 45% and 51%. Egg fertility and hatching rates for 10 wild nests (201 eggs) on Luzon were comparatively higher at 75% and 70%, respectively, but wild egg hatching success in the Muleta River was 45.5% in one nest. (Van Weerd, 2010)

Development - Life Cycle

temperature sex determination

Reproduction

The mating system of C. mindorensis has not been explicitly investigated, but it is common among crocodilians for males and females to have multiple mates. (Britton, 2003)

Captive female and male Philippine crocodiles begin breeding when they are 1.3 meters and 2.1 meters in length, respectively, and about 15 kilograms. Mating and courtship occur in the dry season from December to May and egg laying occurs between April and August, peaking at the beginning of the rainy season in May or June. Philippine crocodiles lay their second clutch 4 to 6 months after the first, and can lay up to three clutches in a year. Clutch sizes vary between 7 and 33 eggs. Incubation periods in the wild for C. mindorensis are between 65 to 78, and 77 to 85 days in captivity. (Alcala, et al., 1987; Hauswaldt, et al., 2013; Sibal, et al., 1992; Van Weerd, 2010)

Breeding from December to May followed by egg laying between May and August

Range number of offspring

7 to 33

Average number of offspring

25

Range gestation period

4 to 5 months

Average age at sexual or reproductive maturity (female)

10 years

Average age at sexual or reproductive maturity (male)

15 years

Generally, female Philippine crocodiles build either hole nests, mound nests, or a combination of the two on river or pond banks that are 4 to 21 meters from the edge of the water. Mound nests are built during the dry season and typically consist of dried leaves, twigs, bamboo leaves, and soil, with a mean height of 55 cm, length of 2 m and width of 1.7 m (based on 4 nests in Luzon). After egg laying males and females take turns watching the nests, and females routinely visit their nests either early in the morning or late in the afternoon. Parental care by the female was observed at Silliman University in captivity for three months after hatching, but this has yet to be observed in wild Philippine crocodiles. (Hinlo, 2010; Sibal, et al., 1992; Van Weerd, et al., 2006; Van Weerd, 2010)

Lifespan/Longevity

Data on the lifespan of C. mindorensis are lacking but crocodilians are thought to live as long as 70 to 80 years. (Britton, 2003)

Behavior

Philippine crocodiles have been shown to be quite aggressive towards each other in captivity. Juveniles have displayed intra-speciﬁc aggressiveness in the wild and, according to field observations in northern Luzon, establish individual territories through aggressive interactions in their second year. However, intra-specific aggressiveness has not been observed among adults or between size or age classes, and sometimes pairs of adult crocodiles are seen basking and swimming together. Crocodiles have also been shown to use individual sites in larger rivers during the drier season when water levels and currents are low but congregate in shallow ponds and creeks during the wet season when river currents are high.

Radio telemetry from a breeding pair revealed the maximum daily movement for the male to be 4.3 km/day and 4 km/day for the female. The male travelled longer distances but less frequently. Habitats favorable to the crocodiles were characterized by waters with average flow velocity, minimum depth and maximum width. Behavioral studies in Dunoy Lake revealed that average distances among wild C. mindorensis, regardless of age, were found to be 20 meters. Areas with lake edge vegetation were found to be preferred by juveniles and hatchlings whereas areas with open water and large logs to bask were preferred by adults. (Schreuder, 2006; Tubbs, 2006; Van Weerd, 2010)

Home Range

Communication and Perception

There has been little study of communication or perception in C. mindorensis so general features applicable to crocodilians has been reported here. It is generally true that crocodilians' skin color can change depending on the environment or the crocodile's mood. Additionally, when the jaw is gaping, bright yellow or orange tongue colors may appear as social or warning signs. Crocodilians can achieve complex vocalizations by forcing exhaled air through a constriction by varying tensions in the muscles lining the glottis, and by expanding the throat via the hyoid apparatus, amplification can be achieved. It is thought that chemical detection is achieved on land when sensory epithelial cells detect chemicals as air passes through the sinuses and achieved in the water by the chemoreceptors lining the tongue. Communication has also been shown to involve pheromones secreted from the chin and paracloacal musk glands. Dome pressure receptors (DPRs) located on head scales, particularly around the jaws, and integumentary sense organs (ISOs), located on the caudal margin of body scales, rapidly alert the crocodile to potential prey by detecting pressure waves created by disturbances of the water surface. Crocodilians can detect frequencies ranging from below 10 Hz to over 10 kHz and, within particular bandwidths, sound pressure levels below -60 dB can be detected. (Britton, 2003)

Food Habits

Prey species that were observed for juvenile Philippine crocodiles included snails, shrimps, dragonﬂies, and small ﬁsh. Prey species for adults included large ﬁsh, pigs, dogs, "civet cats" (probably Asian palm civets (Paradoxurus hermaphroditus), possibly Malayan civets (Viverra tangalunga)), snakes and water birds. True to the crocodile's opportunistic feeding behavior, a variety of prey was taken in captivity including marine and freshwater fish, pork, beef, chicken meat and offal. Smaller prey including shrimp, mince, and white mice were also taken by juveniles and hatchlings. (Van Weerd, 2010)

Predation

Adults of Crocodylus mindorensis have no reported predators other than humans. Larger saltwater crocodiles (Crocodylus porosus) might attack them, but the two species have been observed to co-occur in at least one location on Mindanao. By far the most dangerous predator for this species is Homo sapiens. People kill these animals for their skins and meat, and to protect their livestock and their own safety.

Ecosystem Roles

Very little is known about the ecology of this species, and the surviving wild population is very small. It is likely to be a top predator in freshwater foodwebs in the Philippines.

Economic Importance for Humans: Positive

Humans have killed Philippine crocodiles for their meat and hide; they were extensively harvested for the hides from the 1950s to 1970s. Now they are so rare that there is no organized harvesting. (Banks, 2005)

Economic Importance for Humans: Negative

This species can be a potential threat to livestock, though it is currently too rare to have a significant effect. It is not considered to be a direct threat to humans. In the Philippines it is often confused with the much larger and more dangerous saltwater crocodile (Crocodylus porosus), which is much more dangerous to people. (Banks, 2005; Hauswaldt, et al., 2013; Miranda, et al., 2004)

Conservation Status

The Philippine crocodile is nationally protected by the Republic Act 9147 (the Wildlife Act) since 2001, and the Protected Areas and Wildlife Bureau (PAWB) of the Department of Environment and Natural Resources (DENR) was made responsible for the protection of crocodiles and conservation of their habitat. The DENR created the 'Philippine Crocodile National Recovery Team' (PCNRT) under Special Order 2000-231, which is in charge of recovering C. mindorensis from near extinction. Since the first breeding facility at Silliman University Environmental Centre (SUEC), there have been other breeding programs established to promote the propagation of the Philippine crocodile including the Palawan Wildlife Rescue and Conservation Centre (PWRCC). The DENR also has many agreements with zoos in North America, Europe, and Australia for conservation programs. The Mabuwaya Foundation works through the Crocodile Rehabilitation, Observance, and Conservation (CROC) Project to educate the community about C. mindorensis and encourage its protection by establishing sanctuaries. Additionally, research programs are being implemented with Cagayan Valley Programme on Environment and Development (CVPED) and Dutch and Filipino students to continue adding to the knowledge base of the species. Public awareness is also raised by Mabuwaya via information and education (IEC) campaigns, which use passive (e.g. posters), active (e.g. lectures), and interactive methods (e.g. Q&A discussions). (Alcala, 1997; Banks, 2005; Hauswaldt, et al., 2013; Miranda, et al., 2004; Sumiller, 2000; Van Weerd and Van der Ploeg, 2004; Van Weerd, 2005; Van Weerd, 2010; Van der Ploeg, et al., 2008)

Other Comments

Common names for the Philippine crocodile (Crocodylus mindorensis) include the Philippine freshwater crocodile, buwaya (general Philippines), bukarot (northern Luzon), and the Mindoro crocodile (as per the island it was first discovered on in 1935 by Karl Schmidt).

Contributors

Glossary

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

brackish water

areas with salty water, usually in coastal marshes and estuaries.

carnivore

an animal that mainly eats meat

carrion

flesh of dead animals.

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

diurnal

active during the day, 2. lasting for one day.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

freshwater

mainly lives in water that is not salty.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

insectivore

An animal that eats mainly insects or spiders.

intertidal or littoral

the area of shoreline influenced mainly by the tides, between the highest and lowest reaches of the tide. An aquatic habitat.

island endemic

animals that live only on an island or set of islands.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

male parental care

parental care is carried out by males

marsh

marshes are wetland areas often dominated by grasses and reeds.

migratory

makes seasonal movements between breeding and wintering grounds

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

piscivore

an animal that mainly eats fish

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

vibrations

movements of a hard surface that are produced by animals as signals to others

Hinlo, M. 2010. Population genetics and conservation of the Philippine crocodile : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Conservation Biology at Massey University, Manawatu, New Zealand. Manawatu, New Zealand: Massey University.
Accessed
March 06, 2014
at http://mro.massey.ac.nz/bitstream/handle/10179/2054/02_whole.pdf?sequence=3.

Miranda, J., M. Van Weerd, J. Van der Ploeg. 2004. Devolving crocodile conservation to the local level: the case of the Philippine crocodile conservation in the municipality of San Mariano. Northeast Luzon, the Philippines. 17th Working Meeting of the Crocodile Specialist Group, Gland Switzerland and Cambridge, UK: 309-316.
Accessed
May 15, 2014
at http://www.iucncsg.org/365_docs/attachments/protarea/17th-fd70721f.pdf.

Schreuder, I. 2006. The behavior and ecology of the Philippine crocodile (Crocodylus mindorensis) in its natural habitat. Leiden University and College of Forestry: CVPED. Institute of Environmental Sciences: Cagayan Valley Programme on Environment and Development (CVPED).

Sibal, M., I. Sarsagat, Y. Satake. 1992. Captive breeding of C. mindorensis and C. porosus. Workshop on the prospects and future strategy of crocodile conservation of the two species (C. mindorensis and C. porosus) occurring in the Philippines, Puerto Princesa, Philippines: 36-44.

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This material is based upon work supported by the
National Science Foundation
Grants DRL 0089283, DRL 0628151, DUE 0633095, DRL 0918590, and DUE 1122742. Additional support has come from the Marisla Foundation, UM College of Literature, Science, and the Arts, Museum of Zoology, and Information and Technology Services.